Supporting Information

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1 Supporting Information Constructing MoP y Hetero-nanoparticles Supported Mesoporous N,P-codoped Graphene for Boosting Oxygen Reduction and Oxygen Evolution Reaction Dinh Chuong Nguyen a, Duy Thanh Tran a, Thi Luu Luyen Doan a, Nam Hoon Kim a *, Joong Hee Lee a,b* Synthesis of N,P-Gr material A solution was prepared by dispersing 60 mg of GO into 60 ml of water under sonication for 1 h. After that, 6.6 mg of (NH 4 ) 2 HPO 4 and 5.3 mg Na 2 HPO 2.H 2 O were added into the resulting solution following by continuously stirring for 4 h and then freeze-drying to achieve solid powder. This powder was kept in a quartz boat placed in the CVD system for a subsequent thermal treatment. In this context, a first reaction step was performed at 500 o C in Ar for 4 h with a heating rate of 5 o C and a following step was at 650 o C in H 2 flow for 2 h at a heating rate of 2 o C min -1. After the reaction completed, the CVD system was cooled down to room temperature and final product was then collected for next experiments. Synthesis of N-Gr material For preparing nitrogen doped graphene, 100 mg of GO and 300 mg of melamine were dispersed into 60 ml of water under sonication for 1 h and then followed by a freeze-drying process. The achieved solid was thermally treated at 900 C for 2 h with a heating rate of 5 C min -1 under N 2 atmosphere. After the reaction completed, the final product was collected. 1 Synthesis of P-Gr material For synthesizing P-doped graphene, 100 mg of GO and 500 mg of phosphoric acid were dispersed into 60 ml of water. The solution was sonicated for 1 h and then was freeze-dried. 1

2 After that, the received powder was annealed in a CVD system at 900 C for 2 h with a heating rate of 5 C min -1 under N 2. After the reaction finished, the final product was collected for next experiment. 1 Synthesis of MnP x /N,P-Gr materials Prior to synthesis of the MnP x /N,P-Gr hybrid, a first solution was prepared by dispersing 60 mg of GO and mg of Mn(CH 3 COO) 2.4H 2 O into 60 ml of water under sonication for 1 h. After that, 5.3 mg Na 2 HPO 2.H 2 O were added into the resulting solution, which was continued stirring for 4 h, following by freeze-drying step to achieve a solid powder. This powder was performed by a subsequent two-step calcination process. First reaction step was carried out at 500 o C in Ar for 4 h with a heating rate of 5 o C and second step was at 650 o C in H 2 flow for 2 h with a heating rate of 2 o C min -1. After the reaction finished, the CVD system was cooled down to room temperature and product was collected for next experiment. Synthesis of MoP y /N,P-Gr materials For the synthesis of the MoP y /N,P-Gr hybrid, a first solution was prepared by dispersing 60 mg of GO into 60 ml of water under sonication for 1 h. At the same time, a second solution of 8.8 mg of (NH 4 ) 6 Mo 7 O 24 4H 2 O and g of citric acid in 40 ml of water was prepared under magnetic stirring for 1 h, which was then slowly added into the first solution under continuous stirring for 30 min. After that, 6.6 mg of (NH 4 ) 2 HPO 4 was added into the resulting solution, which was continued stirring for 4 h, following by freeze-drying step to achieve a solid powder. This powder was calcinated with a two-step process, in which first reaction step was at 500 o C in Ar for 4 h with a heating rate of 5 o C and a following step was at 650 o C in H 2 for 2 h with a heating rate of 2 o C min -1. After that the reaction system was cooled down to room temperature and product was received for next experiment. 2

3 Electrochemical Characterizations Calculation of electron transfer number during ORR The Koutecky Levich (K L) plots (J 1 vs. ω 1/2 ) were applied to evaluate the number of electrons transferred (n) at different applied potentials: 2 1 J = 1 J L + 1 J K = 1 Bω J K (1) B = 0.62nFC 0 D v 1 6 (2) where, J, J L, and J K are the measured current density, limiting current density, and kinetic diffusion-limiting current density, respectively; ω is the angular velocity of the RDE (rad s 1 ); F is noted as the Faraday constant; C 0 is known as the saturated oxygen concentration of mol L -1 in 0.1 M KOH; D 0 is the oxygen diffusion coefficient of cm 2 s -1 ); and ν is known as the kinetic viscosity of electrolyte (0.01 cm 2 s -1 ). 3

4 Figure S1. TGA analysis of the MnP y /N,P Gr hybrid. Figure S2. CV curve of the commercial Pt/C in 0.1 M KOH at a scan rate of 50 mv s -1. 4

5 Figure S3. FE-SEM images of GO material. Figure S4. Particle size distribution of (a) MnP y /N,P-Gr, (b) MoP y /N,P-Gr, and (c) MnP x /N,P-Gr. 5

6 Figure S5. (a and b) TEM images of the MoP y /N,P-Gr; (c) STEM and EDS color mapping of (d) Mo, (e) P, (f) C, (g) N; (h) EDAX spectrum of the MoP y /N,P-Gr. 6

7 Figure S6. (a and b) TEM images of the MnP x /N,P-Gr; (c) STEM and EDS color mapping of (d) Mn, (e) P, (f) C, (g) N; (h) EDAX spectrum of the MnP x /N,P-Gr. 7

8 Figure S7. XPS C1s spectrum of GO material. 8

9 Figure S8. (a) Surveyed XPS analysis of the N,P-Gr, MoP y /N,P Gr, MnP x /N,P Gr, and MnP y /N,P Gr; (b) C1s spectrum of N,P-Gr, MoP y /N,P Gr, MnP x /N,P Gr, and MnP y /N,P Gr; (c) Mn2p spectra of the MnP x /N,P Gr and MnP y /N,P Gr; (d) Mo3d spectra of the MoP y /N,P Gr and MnP y /N,P Gr. 9

10 Figure S9. Comparison of ORR performance between N,P-Gr, N-Gr, and P-Gr materials: (a) LSV measurements and (b) Tafel slopes. Figure S10. The mass activities of the MnP y /N,P-Gr based on metal loading and total loading towards ORR at applied potential of 0.6 and 0.85 V and their comparison with Pt/C. 10

11 Figure S11. (a) EIS measurement of different materials and (b) high magnification of semicircle part from EIS measurements in (a). (Inset: The simulated circuit for the EIS measurements). Figure S12. Electrical resistance of the materials studied using 4-point probes method. 11

12 Figure S13. LSV measurements and the corresponding K-L plot of different materials: (a, b) N,P-Gr, (c, d) MnP x /N,P-Gr, and (e, f) MoP y /N,P-Gr. 12

13 Figure S14. (a) The RRDE curves of different materials with of ORR at disk electrode and HO 2 - reoxidation at ring electrode in O 2 -saturated 0.1 M KOH at a scan rate of 10 mv s -1 and rotation speed of 1,600 rpm; (b) Number of electrons transferred and (c) the peroxide anion production in a measured potential range of V. Based on the RRDE results from Fig. S14, the number of electron transferred (n) and the production of HO 2 - fractions ( following equations: X HO 2 ) consistent with ORR process can be evaluated by n = 4I d I d + I r N X OH 2 = 2 I r N I d + I r N Where N is the collection efficiency (N = 0.42), respectively. I r and I d is the ring and disk current, 13

14 Figure S15. The mass activities of the MnP y /N,P-Gr based on metal loading and total loading towards ORR at overpotential of 0.35 and 0.4 V and their comparison with RuO 2 /C. 14

15 Figure S16. The CV measurement of different materials at different scan rates: (a) MnP y /N,P-Gr; (b) MoP y /N,P-Gr, (c) N,P-Gr, and (d) MnP x /N,P-Gr 15

16 MnP y /N,P-Gr Current density (ma cm -2 ) ma cm ma cm ma cm ma cm ma cm Time (s) Figure S17. Chronoamperometric stability of the MnP y /N,P Gr at different applied potentials. 16

17 Figure S18. (a) LSV curves of different materials for HER in 1 M KOH at a scan rate of 10 mv/s; (b) The comparison of over potential for different samples at a current density of 10 and 50 ma cm -2 ; (c) Tafel slopes of different materials. 17

18 Table S1. The absolute Mn and Mo amounts in the hybrid material by ICP analysis Metal Metal loading (wt%) Mo 6.2% Mn 10.7% Total 16.9 % 18

19 Table S2. The content of different element at surface of the hybrid investigated by XPS analysis. Name Start BE Peak BE End BE Height Counts FWHM ev Area (P) CPS.eV At. % C1s Mn2p Mo3d N1s O1s P2p

20 Table S3. Performance comparison of MnP y /N,P-Gr with previous reports towards ORR. Materials V On (V) V Half (V) n Reference N CNS N,P-CNS NPMC S 1 N 6 C S,S -CNT 1000 C Fe-P-C HCNT Mn 2 P Mo 2 C/NPCNFs GMS hybrid Co 2 MnO 4 nanorods ~4 12 FeCo-N/C CoO x NPs/BNG ~4 14 3D Co/NCNTs-Zn/Co ~4 15 Co 9 S ~4 16 Ni 3 FeN/Co,N-CNF ~4 17 ES-CNCo FeTMPPCl ~ 4 19 CoPNi-N/C

21 MnP y /N,P-Gr This work 21

22 Table S4. Performance comparison of MnP y /N,P-Gr with previous reports towards OER. Materials Overpotential at 20 ma cm -2 (mv) Tafel slope (mv dec -1 ) References NiCo 2 S 4 NA/CC NiS/Ni foam FeNi@NC/SBA Co 3 O 4 NCs NiCo 2 O 4 NNs CoP 2 /RGO NiCo LDH Ni 3 N@Ni-Ci NA/CC CoP Co/Co 9 S MnCo 2 S 4 NA/TM CoP/G MoS 2 /Ni-Foam Zn-Co-S/Ti Mesh MnP y /N,P-Gr This work 22

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